Contemporary selector switches of medium voltage switchgear are used for disconnecting a part of an interrupter from a bus bar upon activation of the interrupter. The selector switch comprises a connector element called a knife that, after interruption by means of an in series connected interrupter or breaker has taken place, moves from a first position, in which it is in electric contact with the bus bar, to a second position, in which it is electrically disconnected from the bus bar. In the second position, the switch knife may be electrically connected to ground.
According to prior art the selector switch may be provided in a switchgear housing filled with any suitable electrically insulating gas or gas mixture, such as SF6. The bus bar may have a rectangular cross-section and be made of copper, possibly covered by a layer of silver. A connector element formed by a hooked copper plate is attached to the bus bar at a location corresponding to the location of the switch knife. The connector element comprises a first shank attached to the bus bar, and a second shank extending perpendicularly to the first shank and forming an element to be contacted by the switch knife. The first shank of the connector element may be bolted to the bus bar. The knife normally comprises two parallel shanks or arms that, in the first position in which the knife contacts the second shank of the connector element, overlap said second shank on opposite sides thereof. Preferably, those surfaces of the knife that are assumed to contact the second shank of the connector element are provided with projections, preferably bulges, in order to guarantee a good and reliable contact.
It is an object of the present invention to present a switch device which is of a design that promotes a cost efficient production thereof. A robust design with as few components as possible is also desired.